quote:
Originally posted by WOOCHOW:
My brother just bought a 2002 883R and the owner's manual calls for a 20w-50 or 15w-40 CG or CH rated diesel oil if the Harley brand motor oil is not available.
Two questions, what is so magical about Harley oil, and why would they recommend
a diesel oil over a quality SH gasser oil? Surely its not soot control.
WOOCHOW,
There is many reasons why so many people take such different sides on oils. In the case you're talking about, they are suggesting a thicker oil with higher levels of antiwear/ antiscuffing additives such as the zddp.
Motor cylce oils in general have these higher level of antiwear additives where as the newer gaser oils as you put it, SJ and SL are considerably lower in those additives because of epa and cat converter damage concerns on cars.
These additives are the last line of defense when the base oil shears which happens quite commonly in motorcycles due to the higher rpms and normally the higher heat produced because of being just air cooled. This in one reason why they suggest a higher viscosity oil as well so it takes more to shear the oil out between moving surfaces. Obviously, cold weather isn't much of a concern as not many people will ever ride a bike in 0 or sub 0 weather. I know I never will! So the thicker oil is providing a slight advantage over a thinner one and obviously they feel that a 20w50 is sufficient for flow purposes.
The SH gasser oils also provided higher levels of antiwear but no longer available due to the newer sj/sl certifications.
Now, as an alternative, the cg/ch rated diesel oils are not included in the lowering of antiwear additives as they do not have a cat converter to worry about, therefore, most have the higher levels of antiwear additives like motor cylce oils.
When choosing an oil for a new vehicle, it is always advisable to use the suggested viscosity. In the case of a m/c the only time the api cert's are an issue is if you decide to use something other than a m/c oil. Mobil does have a full synth m/c oil, but I'm not sure what it comes in as for viscosity. amsoil appears to have a full synth mc oil as well.
I myself, use a blend in my harley but it is not classified as a m/c oil. it has a different type of additive that replaces the lower levels of antiwear that were taken out.
Most of the diesel oils that are ch rated, are mineral based. They will provide adaquate protection as long as you don't go wild and extend your oil drains. A full synth will provide you a longer drain interval if you don't like changing it.
Hope that helps.